To make the stuffing topping, cube the cornbread and chop/prep the other stuffing ingredients. Toss in 1/4 cup melted butter, then place on a baking sheet. Sprinkle with a little salt and pepper. Bake at 350°F for 15-20 minutes until lightly toasted.
Boil the noodles according to the package directions to al dente. You want them a little hard in the center still as they will absorb more liquid when they bake in the casserole later.
Finely chop the shallot and mince the garlic. In a large pot, melt the butter. Add the shallot and garlic and cook for just a minute or two. Whisk in the flour, this will become a paste. Season generously with salt and pepper. Then slowly whisk in the milk and stock so it incorporates well (you don't want a bunch of chunks of flour paste floating in the mixture). Then stir in 10 ounces of the shredded cheese. Once it begins to look melted, or mostly melted (sort of stringy on your mixing spoon), then stir in the noodles.
Add this mixture to a greased casserole pan (9x13 or close to that size if it's a different shape, like an oval). Sprinkle with salt and pepper, then top with the remaining cheese and stuffing topping. Cover with aluminum foil and bake at 350°F for 10 minutes. Then remove the aluminum foil from the top and bake another 15 minutes until golden brown and the edges begin to bubble.